SOLID GALLS. 537 



of red currants had been borne by some chance or other on Oak twigs. Tlie galls 

 produced by the Beech-gall gnat (Hormomyia fagi) on the foliage of the Beech 

 resemble small plums, being surrounded by a hard layer which consists of a stone 

 kernel and a layer of cells which might be compared to the fleshy part of a plum. 

 The galls caused by gall -wasps of the genus Aulax on the nutlets of many 

 Labiatse, especially on Nepeta Pannonica and Salvia offi.cinalis also assume the 

 form of stone-fruits. The insect lays its eggs in one of the four nutlets developed 

 at the base of each flower; and within a week this grows into a smooth greenish- 

 yellow ball which has the external appearance of an unripe cherry. A section 

 through it shows that it possesses also the same structure as a cherry, plum, or 

 stone-fruit in general. The succulent outer layer surrounds a hard stony kernel, 

 but in the cavity of the kernel there lies the white larva of the gall-producer 

 instead of the seed. These galls fall oflf just like fruits in July, and lie on the 

 ground during the winter; and the mature insect does not bite an opening in 

 the wall of the gall through which it can emerge until the following year. It 

 has been already remarked at the beginning of this section how strong is the 

 resemblance between apple-fruits and the spherical oak-galls, known as oak-apples, 

 which are produced by various Cynipedes (see fig. 364 2), together with the small 

 red-cheeked galls produced by Rhodites Eglanterim and Nematiis gallarum (see 

 figs. 361^ and 361') on Rose and Willow leaves respectively. Pith-galls which 

 resemble certain dry fruits are very common. Those produced on the green cortex 

 of young Oak twigs by Aphilothrix Sieboldi (see fig. 364^) remind one of the 

 fruits of species of Metrosidevos, those produced by Keuroterus lanuginosus and 

 Spathegaster tricolor on the leaves of the Turkey Oak {Quercus Cerris; see figs. 

 364^^ and 364^*) have a decided similarity to the indehiscent fruits of the Wood- 

 ruff" and of the Goose-grass {Asperula odorata and Galium ApaHne). The 

 "spangle" galls produced on Oak-leaves by the gall -wasps NcuroteriLs fumi- 

 pennis and numismatis resemble the fruits of Omphalodes (see figs. 364^^ and 

 364^2), and the galls on the leaves of Duvaua longifolia produced by an insect 

 Cecidoses Ereraita have the form of a capsule which opens by an operculum (see 

 figs. 362^ and 362^). Like fruits these galls may appear in all imaginable con- 

 ditions with smooth, warted, or rugged surfaces, or covered with woolly or velvety 

 hairs, with bristles or spines, fringes or claws, or even with moss-like outgrowths. 

 The galls with moss-like covering occurring on the Wild Rose have been known 

 from remote times as Bedeguars. They are caused by the Rose-gall wasp (Rhodites 

 Rosce), which deposits its pointed, sometimes hooked eggs early in the spring in 

 the substance of an undeveloped leaf while it is still folded up in the bud. The 

 growth of the leaf becomes altered, the first sign being the development of 

 numerous hairs. The larvae, when they creep out of the eggs, penetrate tleeper 

 into the tissue of the leaf, and it swells out into a solid gall containing as many 

 chambers as there are larvae. Hairs and fringes continue to form on the exterior 

 till those curious structures are formed which were said to ha\'e the power of 

 inducing a peaceful sleep when laid under the pillow. Usually the stalks of the 



